/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.lucene.monitor;

import java.io.IOException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.util.NamedThreadFactory;

public class TestCachePurging extends MonitorTestBase {

  public void testQueryCacheCanBePurged() throws IOException {

    final AtomicInteger purgeCount = new AtomicInteger();
    MonitorUpdateListener listener =
        new MonitorUpdateListener() {
          @Override
          public void onPurge() {
            purgeCount.incrementAndGet();
          }
        };

    try (Monitor monitor = new Monitor(ANALYZER)) {
      MonitorQuery[] queries =
          new MonitorQuery[] {
            new MonitorQuery("1", parse("test1 test4")),
            new MonitorQuery("2", parse("test2")),
            new MonitorQuery("3", parse("test3"))
          };
      monitor.addQueryIndexUpdateListener(listener);
      monitor.register(queries);
      assertEquals(3, monitor.getQueryCount());
      assertEquals(4, monitor.getDisjunctCount());
      assertEquals(4, monitor.getQueryCacheStats().cachedQueries());

      Document doc = new Document();
      doc.add(newTextField("field", "test1 test2 test3", Field.Store.NO));
      assertEquals(3, monitor.match(doc, QueryMatch.SIMPLE_MATCHER).getMatchCount());

      monitor.deleteById("1");
      assertEquals(2, monitor.getQueryCount());
      assertEquals(4, monitor.getQueryCacheStats().cachedQueries());
      assertEquals(2, monitor.match(doc, QueryMatch.SIMPLE_MATCHER).getMatchCount());

      monitor.purgeCache();
      assertEquals(2, monitor.getQueryCacheStats().cachedQueries());

      MatchingQueries<QueryMatch> result = monitor.match(doc, QueryMatch.SIMPLE_MATCHER);
      assertEquals(2, result.getMatchCount());
      assertTrue(purgeCount.get() > 0);
    }
  }

  public void testConcurrentPurges() throws Exception {
    int iters = Integer.getInteger("purgeIters", 1);
    for (int i = 0; i < iters; i++) {
      doConcurrentPurgesAndUpdatesTest();
    }
  }

  private static void doConcurrentPurgesAndUpdatesTest() throws Exception {

    final CountDownLatch startUpdating = new CountDownLatch(1);
    final CountDownLatch finishUpdating = new CountDownLatch(1);

    try (final Monitor monitor = new Monitor(ANALYZER)) {
      Runnable updaterThread =
          () -> {
            try {
              startUpdating.await();
              for (int i = 200; i < 400; i++) {
                monitor.register(newMonitorQuery(i));
              }
              finishUpdating.countDown();
            } catch (Exception e) {
              throw new RuntimeException(e);
            }
          };

      ExecutorService executor =
          Executors.newFixedThreadPool(1, new NamedThreadFactory("updaters"));
      try {
        executor.submit(updaterThread);

        for (int i = 0; i < 200; i++) {
          monitor.register(newMonitorQuery(i));
        }
        for (int i = 20; i < 80; i++) {
          monitor.deleteById(Integer.toString(i));
        }

        assertEquals(200, monitor.getQueryCacheStats().cachedQueries());

        startUpdating.countDown();
        monitor.purgeCache();
        finishUpdating.await();

        assertEquals(340, monitor.getQueryCacheStats().cachedQueries());
        Document doc = new Document();
        doc.add(newTextField("field", "test", Field.Store.NO));
        MatchingQueries<QueryMatch> matcher = monitor.match(doc, QueryMatch.SIMPLE_MATCHER);
        assertEquals(0, matcher.getErrors().size());
        assertEquals(340, matcher.getMatchCount());
      } finally {
        executor.shutdownNow();
      }
    }
  }

  private static MonitorQuery newMonitorQuery(int id) {
    return new MonitorQuery(Integer.toString(id), parse("+test " + id));
  }

  public void testBackgroundPurges() throws IOException, InterruptedException {

    MonitorConfiguration config =
        new MonitorConfiguration().setPurgeFrequency(50, TimeUnit.MILLISECONDS);
    try (Monitor monitor = new Monitor(ANALYZER, Presearcher.NO_FILTERING, config)) {

      assertEquals(-1, monitor.getQueryCacheStats().lastPurged());

      for (int i = 0; i < 100; i++) {
        monitor.register(newMonitorQuery(i));
      }
      assertEquals(100, monitor.getQueryCacheStats().cachedQueries());

      monitor.deleteById("5");
      assertEquals(99, monitor.getQueryCacheStats().queries());

      CountDownLatch latch = new CountDownLatch(1);
      monitor.addQueryIndexUpdateListener(
          new MonitorUpdateListener() {
            @Override
            public void onPurge() {
              // It can sometimes take a couple of purge runs to get everything in sync
              try {
                if (monitor.getQueryCacheStats().cachedQueries() == 99) latch.countDown();
              } catch (IOException e) {
                // Ignore
                throw new RuntimeException(e);
              }
            }
          });

      assertTrue(latch.await(5, TimeUnit.SECONDS));
      assertEquals(99, monitor.getQueryCacheStats().queries());
      assertEquals(99, monitor.getQueryCacheStats().cachedQueries());
      assertTrue(monitor.getQueryCacheStats().lastPurged() > 0);
    }
  }
}
